The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
At present, a communication system covers networks of different architectures, for example, 802.11, 802.16, and 3rd Generation Partnership Project (3GPP). Networks of different architectures are called “heterogeneous networks.”
The IEEE 802.21 (Media Independent Handover Services) protocol provides the link layer information in a heterogeneous network and other relevant network information for the upper layer; the upper layer optimizes handover policies, ensuring that the continuity of the current services is not affected when a terminal is handed over or roams in a heterogeneous network. The IEEE 802.21 protocol supports multiple heterogeneous networks, including IEEE 802.3, IEEE 802.11, IEEE 802.16, 3GPP and 3GPP2, and supports handover of mobile and fixed users and collaboration between a terminal device and a network device.
The IEEE 802.21 protocol defines a mobile node (MN), and provides an architecture that enables transparent service continuity in the case of handover at the link layer in a heterogeneous network. This protocol is based on a mobility management protocol stack within network elements that support the handover. The mobility management protocol stack defines: a group of handover-dependent functions and a new entity named media independent handover function (MIHF) that corresponds to the media independent handover (MIH) layer in the network hierarchy; a group of media-independent service access points (SAPs) and MIHF access related primitives such as media independent event service (MIES), media independent command service (MICS) and media independent information service (MIIS); and media access control (MAC) layer SAPs and relevant primitives intended for each specific access technology. Through the SAPs, the MIHF exchanges messages with other layers and functional planes.
The MIES supports local events and remote events of the same media type. Local events are propagated by the MAC or a radio link to the MIH protocol or Layer 3 Mobility Management Protocol (L3MP) of the local protocol stack. The local protocol stack is located at an access point (AP) or a base station (BS) on the mobile terminal or the network. Remote events are propagated from MIH or L3MP to peer MIH or peer L3MP. The remote events between different media protocol stacks are not supported. An event may indicate the change of a transmission behavior of the data link layer in MAC, predict the status transition, or indicate a network management behavior or command. Sources of an event include the data link layer in MAC, the physical layer (PHY) and the MIHF. Destinations of an event include the MIH of the local protocol stack and/or the MIH of the remote protocol stack. A destination of an event adopts the dynamic registration mechanism and can register a specific event. An event may carry additional context data. Important events include: Link Up (a link setup indication event, sent when a MAC link is set up at a specified link interface and an upper-layer packet can be sent by the L3MP and other upper layers), Link Down (a link break indication event, sent when a MAC link is broken at a specified link interface and no packet is sent on the specified link), Link Detected (a new link is detected), and Link Handover Imminent (link handover is imminent).
The media independent command service (MICS) is adapted for a user to issue commands to control the handover-related link behaviors. The commands are issued from an upper layer to a lower layer in the reference model, including: commands from an upper layer to MIH (from L3MP to MIH, or from a policy engine to MIH), and commands from MIH to its lower layer (from MIH to MAC, or from MIH to PHY). The commands may be issued from a local MIH entity to a remote MIH entity. A command contains decisions made by an upper layer about the lower layers of a local device entity and a remote entity, and is adapted to control behaviors of the lower layers. Important commands include: MIH Capability Discover (adapted to obtain the MIH capabilities of an unused link), MIH Scan (adapted for an upper layer to obtain information about the currently connected or potentially available link), MIH Switch (adapted for an upper layer to hand over an active session from one link to another), MIH Configure (originated by an upper layer to control the behaviors of a lower layer), and MIH Scan (adapted for an upper layer to discover the adjacent POA information).
The media independent information service (MIIS) provides a group of information elements, presenting queries/requests in specified information structures and through specified information transmission mechanisms. Information may be stored in an MIHF entity or an information server (IS) accessible to the MIHF. The network information service capability is accessible through a specific format. The structure and the definition of this format may be presented in an advanced language such as Extensible Mark-up Language (XML). Information services may access static information such as a neighbor information report, which is helpful for network discovery, and may provide dynamic information to optimize the link layer connection between different networks, including link-layer parameters such as channel information, MAC address and security information. Important information includes: Data_Rates (data rate), Location_LatLong (location of the POA, longitude and latitude information), Networks_supported (network types supported by the POA, for example, 802.3, 802.11a, 802.11b, 802.11g, 802.16a, 802.16d, 802.16e, GSM, GPRS, W-CDMA, CDMA2000), and Quality_of_Service (QoS parameter).
FIG. 1 shows an architecture of a heterogeneous network based on the IEEE 802.21 protocol. As shown in FIG. 1, an MIH-enabled terminal is connected to four access networks (WLAN, Wimax, cellular network and wired 802.3 network). The services available from the MIH layer assist the L3MP and other protocol layers in terms of keeping service continuity, adapting to change of QoS, managing battery power, network discovery and network selection, assist the mobile devices in seamless handover between heterogeneous networks, and support upper layer protocols such as Mobile IP to ensure handover and continuity of the session process.
FIG. 2 shows the hierarchy of a heterogeneous network in the prior art. As shown in FIG. 2, a heterogeneous network includes: an access layer 201 consisting of a physical layer and a link layer, an MIHF layer 202, an MIH user layer 203 and a network management entity 204. As a lower layer of the network, the access layer 201 includes an 802.2 or 802.3 access network, a 3GPP access network, a 3GPP2 access network, an 802.11 access network and an 802.16 access network. Each access network is connected to the MIHF layer 202 through an SAP to perform information interaction. As an upper layer, namely, layer 3 or a higher layer in the network, the MIH user layer 203 includes an application layer, a transport layer and a network layer, and is connected to the MIHF layer 202 through an MIH_SAP to perform information interaction. The MIHF layer 202 is connected to the network management entity 204 through an MIH_NMS_SAP (MIH network management system service access point) to perform information interaction. Each SAP includes a group of primitives, which are used for information processing in a specified information exchange format, and helpful for collecting the link layer information and controlling link behaviors in the handover.
FIG. 3 shows the location of an MIHF and key services in a network. As shown in FIG. 3, the MIHF is located between an MIH user layer (layer 3 or a higher layer, for example, Session Initiation Protocol (SIP), MIPV4, MIPV6, and HIP) and a lower layer (layer 2 or a lower layer, for example, 802.3, 802.11, 802.16, 3GPP and 3GPP2). The link layer event sent by the lower layer is transmitted to the MIH user layer after being converted by the MIHF layer into an MIH event. The MIH command issued by the MIH user layer is transmitted to the lower layer after being converted by the MIHF layer into a link layer command. For example, the L3MP manages, decides and controls the status of the lower-layer interface by using the events, commands and information services provided by the MIH protocol.
FIG. 4 shows the hierarchy of the MIH reference model. As shown in FIG. 4, the hierarchy of the MIH reference model includes a user hierarchy and a network hierarchy. The user communicates with the network through an MIH protocol. Moreover, an MIH-enabled mobile terminal receives the asynchronous operation commands such as event service from the lower layer.
Based on the foregoing heterogeneous network, the user can be handed over in the network. The handover methods adopted by the IEEE 802.21 protocol include hard handover and soft handover. The main factors that affect handover include: service continuity, application type, QoS, network discovery, network selection, security, power management, handover performed with the movement of the terminal, and handover policies.
In view of the power management in the foregoing factors, IEEE 802.21 proposes to use different power configuration modes in different working conditions.
In the current heterogeneous networks based on the IEEE 802.21 protocol, however, no handover policy is available for the terminal to select a lower-layer network connection automatically according to the current power status, and the power consumption of different networks is not taken as a decisive factor. Therefore, the terminal is unable to learn the power consumption parameters of various networks and unable to select a lower-layer network connection automatically according to the power consumption and the current power status. For example, if the battery power is low when a multi-mode terminal is setting up a network connection through an 802.11-based WiFi interface, the terminal is unable to notify the system to shut down the WiFi interface or automatically select a less power-consuming interface (for example, GSM/GPRS) for connecting so as to prolong the service time.